staging: fsl-dpaa2/eth: Remove obsolete reference

Commit 2b7c86eb ("staging: fsl-dpaa2/eth: Don't enable FAS on Tx")
removed the status field from the TX confirm frame annotation,
but a reference to it remained in the description of free_tx_fd().
Remove it.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>